Injection device

ABSTRACT

The present invention concerns an injection device with a housing adapted to receive a syringe having a discharge nozzle, the housing having an indicator opening. There is a trigger and a forward drive arranged to act upon the syringe on actuation of the trigger to advance the syringe from a retracted position to an extended position thereby discharging the contents of the syringe through the discharge nozzle. A support member is in contacting juxtaposition with the housing and a return drive is supported by the support member and arranged to act upon the syringe after the contents of the syringe has been discharged so that the syringe can be withdrawn from the extended position to the retracted position. Advantageously, the support member is arranged in the housing so that the second drive does not obscure an inspection of the contents of the syringe through the indicator opening. Hence, it can be clearly determined whether the contents of the syringe have been expelled from the syringe.

FIELD OF INVENTION

The present invention relates to an injection device of the type thatreceives a syringe, extends it, discharges its contents and thenretracts it automatically. Devices of this general description are shownin WO 95/35126 and EP-A-0 516 473 and tend to employ a drive spring andsome form of release mechanism that releases the syringe from theinfluence of the drive spring once its contents are supposed to havebeen discharged, to allow it to be retracted by a return spring. Theinitial action of the drive spring is typically controlled by means of atrigger. Depression of the trigger causes the drive spring to becomeoperative.

BACKGROUND OF INVENTION

It is not uncommon for an injection device that has been previously used(i.e. a device which has been triggered and therefore has had thecontents of its syringe discharged) to be mistaken for a device whichhas not been used. Although injection devices of this type may includean interlock to prevent further triggering of the device, marketresearch has shown that it is beneficial for an injection device toprovide some form of indication that the contents of the syringe hasbeen completely discharged. This way, a user is able to determineimmediately by visual inspection whether an injection device has beenused. In particular, it has been shown that users of injection devicesprefer a visual inspection of the actual syringe to see whether itscontents has been discharged. With current injection devices, the returnspring often surrounds the syringe thereby obstructing the view of thecontents of the syringe. Furthermore, the sight of a return springsurrounding a syringe can be unappealing to a user of an injectiondevice.

It is therefore an aim of the present invention to provide an injectiondevice which gives a clear indication of whether the contents of asyringe has been discharged without the inner mechanical elements of thedevice being seen by a user. As ever, the simplest and cheapest way ofachieving this is sought.

SUMMARY OF THE INVENTION

In view of the foregoing, according to the present invention, there isprovided a housing adapted to receive a syringe having a dischargenozzle, the housing having an indicator opening; a forward drivearranged to act upon the syringe on actuation to advance the syringefrom a retracted position to an extended position thereby dischargingthe contents of the syringe through the discharge nozzle; a return drivearranged to act upon the syringe after the contents of the syringe havebeen discharged to withdraw the syringe from the extended position tothe retracted position, characterised in that the return drive isarranged in the housing so that it does not obscure an inspection of thecontents of the syringe through the indicator opening. Thus, there is aclear indication through the indicator opening of whether the contentsof the syringe has been discharged. In addition, the inner mechanicalelements of the device cannot be seen by a user. Furthermore, theindicator opening provides a large window which is not obscured andtherefore allows the contents of the syringe to be checked for turbidityand the presence of particles indicating whether the contents of thesyringe is safe to be injected.

In one embodiment of the present invention, the injection devicecomprises a support member which is in contacting juxtaposition with thehousing and the return drive is supported by the support member.

Preferably, the support member is transparent and positioned between theindicator opening and syringe. This way, the internal contents of thesyringe can be viewed. Before actuation, the liquid contents of thesyringe will be viewable through the indicator opening. Transparentmaterial that may be used for the support member is any rigid materialwhich allows light to pass through (e.g. clear or opaque materials).

The support member may comprise a cylindrical insert dimensioned tocontain the syringe; and a support surface for the return drive.

In one embodiment of the present invention, a first end of the returndrive is in contacting juxtaposition with the support surface and asecond end of the return drive is in contacting juxtaposition with thesyringe. In a second embodiment of the present invention, the syringecarrier is dimensioned to contain the syringe, the cylindrical insert isdimensioned to contain the syringe carrier and a first end of the returndrive is in contacting juxtaposition with the support surface and asecond end of the second drive is in contacting juxtaposition with thesyringe carrier.

Advantageously, the indicator opening is positioned so that a plunger ofthe syringe is viewable through the indicator opening when the contentsof the syringe has been discharged. After discharge of the contents ofthe syringe, the plunger, which may be coloured with an easilyidentifiable colour, will be viewable through the indicator opening toindicate that the injection device has been used.

Preferably, the return drive is a helical spring surrounding at leastpart of the syringe. By surrounding the syringe with the helical spring,a single spring can be employed which is large enough to have asufficient spring constant to return the syringe into its retractedposition.

Advantageously, the indicator opening comprises a transparent insertwhich allows inspection of the syringe without the syringe beingdamaged.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described by way of example with reference tothe accompanying drawings, in which:

FIG. 1 shows in perspective an injection device of the type to which thepresent invention is applicable;

FIG. 2 shows in section the injection device of FIG. 1 before actuation;and

FIG. 3 shows in section the injection device of FIGS. 1 and 2 afteractuation.

DETAILED DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an injection device 110 having a housing 112 with aproximal end 101 and a distal end 102. The housing 112 has a trigger 111which projects through the housing 112 and which can be actuated bypressing down on its upper surface 111 a. There is a indicator opening113 in the housing located adjacent the proximal end 101.

FIG. 2 shows the housing 112 containing a hypodermic syringe 114 ofconventional type, including a syringe body 116 terminating at one endin a hypodermic needle 118 and at the other in a flange 120. Theconventional plunger and bung that would normally be used to dischargethe contents of the syringe 114 manually have been removed and replacedwith a drive element 134 which includes a bung 134 a. This drive element134 constrains a drug 124 to be administered within the syringe body116. Whilst the syringe illustrated is of hypodermic type, this need notnecessarily be so. Transcutaneous or ballistic dermal and subcutaneoussyringes may also be used with the injection device of the presentinvention. As illustrated, the housing includes a return drive whichhere takes the form of a compression return spring 126 that biases thesyringe 114 from an extended position in which the needle 118 extendsfrom an aperture 128 in the housing 112 to a retracted position in whichthe discharge nozzle 118 is contained within the housing 112.

The housing 112 includes a support member which, as shown in FIG. 2,takes the form of a cylindrical insert 122. The cylindrical insert 122has, on its inner surface, a support surface 122 a which connects withone end of the return spring 126. The other end of the return spring 126acts on the syringe 114 via a syringe carrier 127. The support surface122 a is provided, as shown in FIG. 2, by a rim on the inner surface ofthe cylindrical insert 122. The support surface 122 a is positionedbeyond the indicator opening 113 away from the proximal end 101 of thehousing 112. The return spring 126 connects with the support surface 122a on its end which is located away from the proximal end 101 of thehousing 112 and its other end acts on the syringe carrier 127 beyond thesupport surface 122 a from the proximal end 101 of the housing 112. Thisway, the return spring 126, which surrounds the syringe 114 and syringecarrier 127, cannot be seen through the indicator opening 113 at anytime before, during or after triggering of the injection device 110. Thecylindrical insert 122 forms a window in the indicator opening 113formed from transparent material so that the contents of the syringe 114can be viewed through the indicator opening 113.

At the other end of the housing 112 is a forward drive, which here takesthe form of a compression drive spring 130. Drive from the drive spring130 is transmitted via a multi-component drive to the syringe 114 toadvance it from its retracted position to its extended position anddischarge its contents through the needle 118. The drive accomplishesthis task by acting directly on the drug 124 and the syringe 114. Staticfriction between the drive element 134 and the syringe body 116initially ensures that they advance together, until the return spring126 bottoms out or the syringe body 116 meets some other obstruction(not shown) that retards its motion.

The multi-component drive between the drive spring 130 and the syringe114 consists of three principal components. A drive sleeve 131 takesdrive from the drive spring 130 and transmits it to a first driveelement 132. This in turn transmits drive via a damping fluid to asecond drive element, the drive element 134 already mentioned.

The first drive element 132 includes a hollow stem 140, the inner cavityof which forms a collection chamber 142 in communication with a vent 144that extends from the collection chamber through the end of the stem140. The second drive element 134 includes a blind bore 146 that is openat one end to receive the stem 140 and closed at the other. As can beseen, the bore 146 and the stem 140 defining a fluid reservoir 148,within which the damping fluid is contained.

The trigger 111, when operated, serves to decouple the drive sleeve 131from the housing 112, allowing it to move relative to the housing 112under the influence of the drive spring 130. The operation of the deviceis then as follows.

Initially, the drive spring 130 moves the drive sleeve 131, the drivesleeve 131 moves the first drive element 132 and the first drive element132 moves the second drive element 134. The second drive element 134moves and, by virtue of static friction and hydrostatic forces actingthrough the drug 124 to be administered, moves the syringe body 116against the action of the return spring 126. The return spring 126compresses and the hypodermic needle 118 emerges from the exit aperture128 (shown in FIG. 3) of the housing 112. This continues until thereturn spring 126 bottoms out or the syringe body 116 meets some otherobstruction (not shown) that retards its motion. Because the staticfriction between the second drive element 134 and the syringe body 116and the hydrostatic forces acting through the drug 124 to beadministered are not sufficient to resist the full drive force developedby the drive spring 130, at this point the second drive element 134begins to move within the syringe body 116 and the drug 124 begins to bedischarged. Dynamic friction between the second drive element 134 andthe syringe body 116 and hydrostatic and hydrodynamic forces now actingthrough the drug 124 to be administered are, however, sufficient toretain the return spring 126 in its compressed state, so the hypodermicneedle 118 remains extended.

Before the second drive element 134 reaches the end of its travel withinthe syringe body 116, so before the contents of the syringe have fullydischarged, protrusions (not shown) on the first drive element 132 reacha constriction 137 within the housing 112. The constriction 137 movesthe protrusions inwards so that the first drive element 136 is no longercoupled to the second drive element 134. Once this happens, the firstdrive element 136 no longer acts on the second drive element 134,allowing the first drive element 132 to move relative to the seconddrive element 134.

Because the damping fluid is contained within a reservoir 148 definedbetween the end of the first drive element 132 and the blind bore 146 inthe second drive element 134, the volume of the reservoir 146 will tendto decrease as the first drive element 132 moves relative to the seconddrive element 134 when the former is acted upon by the drive spring 130.As the reservoir 148 collapses, damping fluid is forced through the vent144 into the collection chamber 142. After release of the drive spring130, some of the force exerted by the drive spring 130 does work on thedamping fluid, causing it to flow though the constriction formed by thevent 144; the remainder acts hydrostatically through the fluid andthrough friction between the first and second drive elements 132, 134,thence via the second drive element 134. Losses associated with the flowof the damping fluid do not attenuate the force acting on the body ofthe syringe to a great extent. Thus, the return spring 126 remainscompressed and the hypodermic needle remains extended.

After a time, the second drive element 134 completes its travel withinthe syringe body 116 and can go no further. At this point, the contentsof the syringe 114 are completely discharged and the force exerted bythe drive spring 130 acts to retain the second drive element 134 in itsterminal position and to continue to cause the damping fluid to flowthough the vent 144, allowing the first drive element 132 to continueits movement.

Before the reservoir 148 of fluid is exhausted, flexible latch arms 133linking the drive sleeve 131 with the first drive element 132 are nolonger forced to engage the drive sleeve 131 by protrusions 133 a on thesecond drive element 134. Once this happens, the drive sleeve 131 actsno longer on the first drive element 132, allowing them to move relativeto each other. At this point, of course, the syringe 114 is released,because the forces developed by the drive spring 130 are no longer beingtransmitted to the syringe 114, and the only force acting on the syringewill be the return force from the return spring 126. Thus, the syringe114 is now returned to its retracted position and the injection cycle iscomplete.

All this takes place, of course, only once the cap 115 has been removedfrom the end of the housing 112. As can be seen from FIG. 2, the end ofthe syringe 114 is sealed with a boot 123.

FIG. 3 shows the injection device 110 after actuation of the injectioncycle is complete. The second drive element 134 is located within thesyringe body 116 so that it can be viewed through the indicator opening113. The second drive element 134 is held within the syringe body 116,even though the drive sleeve 131 has been disengaged from themulti-component drive, by forked lugs 210 located on the second driveelement 134. The forked lugs 210 have been forced through theconstriction 137 so that they prevent rearward movement (i.e. movementin a direction from the proximal end 101 to the distal end 102) of thedrive element 134. Thus, the drive element 134 is held in place withinthe syringe 116 so that it can be viewed through the indicator opening113. The presence of the second drive element 134 in the syringe body116 after discharge of the drug 124 acts as an indicator to a user ofthe device 110 that the device 110 has been operated.

It will of course be understood that the present invention has beendescribed above purely by way of example and that modifications ofdetail can be made within the scope of the invention.

The invention claimed is:
 1. An injection device, comprising: a housingthat receives a syringe having a discharge nozzle, the housing having anindicator opening; a forward drive arranged to act upon the syringe onactuation to advance the syringe from a retracted position to anextended position thereby discharging contents of the syringe throughthe discharge nozzle; a return drive arranged to act upon the syringeafter the contents of the syringe have been discharged to withdraw thesyringe from the extended position to the retracted position, whereinthe return drive is arranged in the housing so that the return drivedoes not obscure an inspection of the contents of the syringe throughthe indicator opening; and a support member in contacting juxtapositionwith the housing, wherein the return drive is supported by the supportmember and the support member is formed of a transparent material andpositioned between the indicator opening and syringe.
 2. An injectiondevice according to claim 1 wherein the support member comprises: acylindrical insert dimensioned to contain the syringe; and a supportsurface for the return drive.
 3. An injection device according to claim2, wherein a first end of the return drive is in contactingjuxtaposition with the support surface and a second end of the returndrive is in contacting juxtaposition with the syringe.
 4. An injectiondevice according to claim 2, further comprising a syringe carrierdimensioned to contain the syringe, wherein the cylindrical insert isdimensioned to contain the syringe carrier and wherein a first end ofthe return drive is in contacting juxtaposition with the support surfaceand a second end of the return drive is in contacting juxtaposition withthe syringe carrier.
 5. An injection device according claim 1 whereinthe indicator opening is positioned so that a plunger of the syringe isviewable through the indicator opening when the contents of the syringehas been discharged.
 6. An injection device according to claim 1 whereinthe return drive is a helical spring surrounding at least part of thesyringe.
 7. An injection device according to claim 1 wherein theindicator opening comprises a transparent window.